Ammonium nitrate-aliphatic hydrocarbon-urea clathrate explosives



United 4 States Patent 3,135,637 AMMONHJM NlTRATE-ALHPHAHC HYDROCAR- BGN-UREA CLA'IHRATE EXPLGSIVES Charles M. Salier, J12, Levittown, Pa., assignor to Thiokol Chemical Corporation, Bristol, Pa, a corporation of Delaware No rawing. Filed Nov. 15, 1962, Ser. No. 238,037

9 Claims. (Ci. 149-46) This invention relates to blasting explosives and more particularly to explosives in which ammonium nitrate, aliphatic hydrocarbons and urea are the chief constituents.

For some time now, mixtures of ammonium nitratealiphatic hydrocarbon explosives have been utilized in commercial applications, such as, in mining and in quarrying. These explosive mixtures are mixed just prior to detonation. The reason for this is that the sensitivity of these explosives greatly decreases upon standing or storage for any extended length of time. This loss of sensitivity is believed to be caused by the separation of the aliphatic hydrocarbon component from the ammonium nitrate apparently because of gravity. The segregation of the aliphatic hydrocarbon component into a distinct phase desensitizes the explosive mixture to such an extent that no substantial explosive force is released upon detonation.

This invention overcomes the above drawbacks of the prior art explosive mixtures by providing ammonium nitrate aliphatic hydrocarbon explosive mixtures which are stabilized in one instance through the addition of a urea-aliphatic hydrocarbon clathrate to the ammonium nitrate-based explosive and in another instance by in situ formation of the clathrate. By these means the separation of the aliphatic hydrocarbon from the ammonium nitrate is prevented such that the explosive mixture retains a constant level of reactivity toward detonation. As a result, the explosive mixture of this invention may be mixed and stored prior to actual use, safely handled and detonated when needed.

Thus it is an object of this invention to prepare an ammonium nitrate-based explosive mixture that can be safely prepared prior to use at the blasting site.

- It is another object of this invention to prepare ammonium nitrate-based explosives which retain a constant high level of sensitivity toward detonation for appreciable periods of time. Yet another object of the invention is to prepare a urea-aliphatic hydrocarbon clathrate additive which retards the separation of the hydrocarbon phase from homogeneous ammonium nitrate-aliphatic hydrocarbon containing explosives. Additional objects of this invention will become apparent as this invention is more fully defined.

These objects are accomplished as follows: a solution of urea in an aliphatic alcohol is combined With an aliphatic hydrocarbon under moderate heat and vigorous stirring conditions, until a homogeneous clathrate is ob tained. The resultant urea-aliphatic hydrocarbon clathrate is then mixed with the ammonium nitrate component to form the explosive mixture of this invention.

The proportions of the chief constituents of the inventive explosive composition which can be employed to yield a satisfactory composition are as follows: 75-98 parts be weight of ammonium nitrate and 25-2 parts by weight of the urea-aliphatic hydrocarbon clathrate.

Especially good results insofar as inhibiting the loss of sensitivity toward detonation are obtained in explosive compositions consisting of 80 to 94 parts by weight of ammonium nitrate and 20 to 6 parts by weight of the urea-aliphatic hydrocarbon clathrate.

The urea-aliphatic hydrocarbon clathrate in turn comprises 36 parts by weight of the urea constituent for each part by weight of the aliphatic hydrocarbon used ICC with 4-5 parts by weight of urea to 1 part by weight of aliphatic hydrocarbon, representing the preferred ratio;

In practicing my invention, the following procedure can be employed: Theurea-aliphatic hydrocarbon clathrate is produced by heating together a well-mixed dispersion of a predominantly aliphatic hydrocarbon and a solution of urea in an alkanol at moderately low temperatures with constant mixing until the urea-aliphatic hydrocarbon constituents are homogenously mixed. The clathrate, a homogeneous, crystalline solid, formed by the urea-aliphatic hydrocarbon mixture is then combined with the ammonium nitrate to yield ultimately a homogenous explosive mixture.

During the formation of the urea-aliphatic hydrocarbon clathrate, the temperature is kept below 65 C. However, it has been found that especially favorable results are obtained in the narrower range of 55 C. to 60 C. The aliphatic hydrocarbon constituents of the clathrate are defined herein as including paraffinic alkanes or aliphatic hydrocarbons as well as the so called aliphatic fatty acids. Thus, these aliphatic hydrocarbons may be chosen from a number of saturated and unsaturated, straightchain or branched-chain aliphatic hydrocarbons and aliphatic fatty acids. For example, satisfactory results have been obtained using the following: decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonodecane, and eicosane. An especially convenient source of hydrocarbons for this purpose are the so called aliphatic hydrocarbon fractions ordinarily produced during oil refinery operations such as cracking and the like. However, even fuel oil fractions enriched with aliphatic hydrocarbons are satisfactory, as well as fatty acids such as palmitic, stearic, oleic, linoleic and linolenic derived from petroleum refining or other sources. As indicated above, other aliphatic alcohols can be used. Satisfactory results are obtained using such alcohols as ethanol, methanol, isopropanol and propanol among others.

Generally, a homogeneous system is obtained after five minutes of mixing with one minute being the average time. The crystalline, solid urea-aliphatic hydrocarbon clathrate is then combined with the ammonium nitrate at substantially ambient temperature using a mixer with a non-explosive motor in a well-known manner employed in the explosives art. The order of combining the clathrate and ammonium nitrate compounds is not critical.

The invention will be further illustrated by the description in connection with the following specific examples of the practice of it. In these examples and elsewhere proportions are expressed in parts by weight unless otherwise indicated.

EXAMPLE 1 Preparation of the Explosive Compositions of This Invention To a suitable reaction vessel equipped with heating, cooling and stirring means is added40 parts by weight of urea dissolved in 160 parts by weight of anhydrous methanol. To g. of this urea-methanol solution is slowly added, at room temperature with stirring, 3.5 g. of an aliphatic hydrocarbon fraction containing primarily 0 -0 paraffinic hydrocarbons. After the addition is complete, the crystalline urea-aliphatic hydrocarbon clathrate forms and is separated by filtration cooled to room temperature, dried and combined with 94 parts by weight of fine grind ammonium nitrate. A homogeneous mixture is obtained.

EXAMPLE 2 Using the equipment and technique described in Example 1, the procedure of Example 1 is repeated except that 3.5 g. of .dodecane is used instead of the paraflinic is identical to that prepared in Example 5.

. a I fraction. Upon the addition of ammonium nitrate, mixing is'continued until a homogeneous mixture is obtained.

EXAMPLE 3 EXAMPLE 5.

Preparation of the Inventive Composition by the in Situ Preparation of Urea-Aliphatic Hydrocarbon Clathrate 6 Using the components described in'Example '1, the urea aliphatic hydrocarbon clathrate is prepared in situ as follows: t

94 g. of ammonium nitrate and 3.5 g. of an aliphatic hydrocarbon are combined in an appropriate mixer resulting in a homogeneous mixturej To this mixture is added 75 g. of a urea-methanol solution prepared in ac-' cordance with the procedure set forth in Example'l. The mixture is stirred at room temperature for about ten minutes until a urea-hydrocarbon clathrate is formed. 'The excess urea-methanol solution is filtered off and the remaining solid' mixture is dried in air at ,room temperature. The resultant explosive mixture has identical characteristics to the explosive. mixture prepared in Example 1.

EXAMPLE 6 Using the equipment and technique described in Example 5, the procedure is repeated except that the amount of methanol used is greatly decreased. Inthis example, 40 the 15 g. portion of'ureads moistened with methanol. Since there is no liquid phase, no filtration or drying steps are necessary as was the case in Example 5. When the mixing is completed, the resultant explosive mixture -EXAMPLE'7 I 7 Using the equipment and technique described in Example 5, the following modificationsare made shownbelow. 7 V

' Ammonium V Urea, Aliphatic Nitrate, parts by Hydrocarparts by. weight bon, parts .weight. by weight The resultant explosive mixture is identical to that prepared in Example 5. V

' EXAMPLES Again the equipment and technique described in Example 5 are used. The modifications are shown below.

Ammonium Urea, Aliphatic Nitrate, parts by Hydrocarparts by Weight bon, parts weight a by weight The resultant explosive mixture has identical characteristics .to that p'repared in Example 5.

I EXAMPLE 9 Preparation of Farther Explosive Compositions Again the equipment and technique described in the first two examples are used. The modifications shown below are made.

Ammonium Nitrate, Alcohol Aliphatic Urea V Hydrocarbon Same as in Examp 1.

Fine grind ethanol dodecaneu n kerosene Agricultural grade- Do oleic acid of the aliphatic hydrocarbon components. None ofthe explosive mixtures exhibited any tendency toward aliphatic.

hydrocarbon separation. As a control, twosamples of ammonium nitrate-aliphatic hydrocarbonv mixture prepared according to the prior art method were stored under the same condition and for the same period of time.

In both instances, the prior art explosive composition leakedialiphatic hydrocarbon badly indicating extreme segregation.

Bl Constant sensitivity toward detonation-The ex plosive mixtures prepared in Examples 1 to 9 are'detonated immediately after preparation, and after prolonged storage, respectively; 'The testing procedure used was the Picatinny Arsenal impact test 'and is described in TM 91410,pages 43-47, and is the one described herein below. The prior. art ammonium nitrate-aliphatic hydrocarbon explosive mixture is: used asa controli Deto nation is made as before immediately after preparation and after prolonged storage." One pound chargeswere prepared consisting of the ammonium nitrate urea-aliphatic-hydrocarbon mixture of theinvention; A standard electrically fired No. 8 detonatoi' was used to which 1 a five jgram tetryl'pell'et was taped and centered in the explosive-mixtureL The test results appear below:

' Sensitivity 'Product After After 30 days Preparation storage Example 1 Explosion-.- Explosion. Example 2 do Do. Examplefi; Do.

- Example 4 D0. Example 5-- Do. Example 6-- Do. Example 7-- Do. Example 8- t Do. Example 9-- Do. Prior'Ar N o Explosion.

As can be seen from the above data, the products of the invention are superior to the prior art in both freetivity toward detonation What is claimed is:-

dom irom segregation and in maintaining constant sensiof ammonium nitrate and a urea-aliphatic hydrocarbon clathrate, .s'aid aliphatic hydrocarbon clathrate being sepound selected from the group consisting of aliphatic.

hydrocarbons and aliphaticfatty acids. a

In each instance. homogenous mixtures-are obtained. Stability and Sensitivity Toward Detonation of'the 1. A blasting explosive comprising .a' reaction mixture lected from the group consisting of urea-aliphatic hy- V 2. The composition of claim 1 in which 94 parts by weight of ammonium nitrate component is combined with 6 parts by weight of urea-aliphatic hydrocarbon clathrate.

3. The composition of claim 1 wherein the aliphatic hydrocarbon constituent of the ureaaliphatic hydrocarbon clathrate is eicosane.

4. The composition of claim 1 wherein the aliphatic fatty acid constituent of the urea-aliphatic fatty acid clathrate is oleic acid.

5. The composition of claim 1 wherein the aliphatic hydrocarbon constituent of the urea-aliphatic hydrocarbon clathrate is dodecane.

6. The composition of claim 1 wherein the aliphatic hydrocarbon constituent of the urea-aliphatic hydrocarbon clathrate is kerosene.

7. The composition of claim 1 wherein the aliphatic hydrocarbon constituent of the urea-aliphatic hydrocarbon clathrate is 1-decene.

8. The process of stabilizing ammonium nitrate-aliphatic hydrocarbon explosive mixtures comprising the step of combining ammonium nitrate with a urea-aliphatic hydrocarbon clathrate, said aliphatic hydrocarbon clathrate being selected from the group consisting of urea-aliphatic hydrocarbon clathrates and urea-aliphatic fatty acid clathrates, said clathrate being prepared by mixing 3 to 6 parts by weight of urea with each part of aliphatic hydrocarbon, so that the resulting ammonium nitrate-urea-aliphatic hydrocarbon clathrate comprises to 98 parts by weight of ammonium nitrate and 25 to 2 parts by weight of urea-aliphatic hydrocarbon clathrate.

9. The process of stabilizing ammonium nitrate-aliphatic hydrocarbon explosive mixtures, said explosive mixtures containing 2 to 6 parts by weight of aliphatic hydrocarbon to each 100 parts by weight of ammonium nitrate which comprises the step of intimately mixing said explosive compositions with 10 to 20 parts by weight of urea.

References Cited in the file of this patent UNITED STATES PATENTS Carey Apr. 4, 1944 2,455,205 Whetstone et al Nov. 30, 1948 

1. A BLASTING EXPLOSIVE COMPRISING A REACTION MIXTURE OF AMMONIUM NITRATE AND A UREA-ALIPHATIC HYDROCARBON CLATHRATE, SAID ALIPHATIC HYDROCARBON CLATHRATE BEING SELECTED FROM THE GROUP CONSISTING OF UREA-ALIPHATIC HYDROCARBON CLATHRATES AND UREA-ALIPHATIC HYRATES IN THE PROPORTION OF 75 TO 98 PARTS BY WEIGHT OF AMMONIUM NITRATE AND 25 TO 2 PARTS WEIGHT OF SAID UREA CLATHRATE, SAID UREA CLATHRATE CONSISTING OF 3 TO 6 PARTS BY WEIGHT OF UREA TO EACH PART OF AN ALIPHATIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC HYDROCARBONS AND ALIPHATIC FATTY ACIDS. 